The present invention is directed to a dental percussion instrument comprising an instrument housing designed as a handpiece, a ram having a test head at one end and being mounted for axial movement in the instrument housing and an electromagnetic drive means for shifting the ram axially in the housing.
Percussion instruments are known. In one type, a compression spring is arranged concentrically relative to the ram to act as a drive means and this type is disclosed in German Pat. No. 26 17 779. In another type, a magnetic coil is the drive means for moving a ram in the housing and this type is disclosed in U.S. Pat. No. 4,499,906.
In order to meet the demands of being able to execute a reliable diagnosis with the instrument even at locations in the mouth of the patient which are relatively poorly accessible, a desired aim is to keep the instrument as slim as possible. Thus, it is desirable to have as small a diameter as possible precisely in the front region of the instrument which is where the drive is situated in the known structures.
Another problem is to move the ram with a constant speed after the drive has been shut off and until impact against the test subject occurs. Since the ram in the known instruments comprises a part having a considerable cross-sectional enlargement as seen over its length and this increased cross-sectional enlargement not only increases the diameter but also results in an undesirable braking effect, it is not possible to obtain the constant speed with the desired precision for the known instruments.